There are situations where oil in the ground overlies water or a basement rock and can be recovered by unconventional means.
An example of such a situation is a layer of light oil overlying water in a shallow loose or lightly cemented sand deposit. For example, if the sand is a sand dune area adjacent to a large body of water such as a lake or an ocean, the layer of oil can be formed by an oil spill which collects and floats on the water table but under the surface of the sand dune. The oil spill can result, for example, from a breach or leak in an underground pipeline that goes undetected for a period of time.
Another example of such a situation is a layer of heavy oil or bitumen in a shallow lightly cemented oil sand deposit overlying either a layer of water or lying directly on a basement rock. Such situations occur in many shallow heavy oil or bitumen deposits (that is, oil sands deposits under no more than a few hundred meters of overburden). In some cases, production of heavy oil by cold flow may be feasible. In other cases, the heavy oil or bitumen may have to be mobilized by injection of steam or diluent.
While it may be possible to drill wells from the surface or to strip off the overburden to recover the hydrocarbon of interest, there may be surface restrictions preventing these approaches. For example, the hydrocarbon deposit may be under a lake, a river valley, a town, a protected wildlife habitat, a national park or the like.
There remains, therefore, a need for a method and means to recover the oil from above the underlying aquifer or basement rock by methods that minimize surface disturbance.